Reverse First K elements of Queue Python

PROGRAM TO REVERSE THE FIRST K ELEMENTS OF A QUEUE

from queue import Queue

 

# Function to reverse the first K

# elements of the Queue

def reverseQueueFirstKElements(k, Queue):

    if (Queue.empty() == True or

             k > Queue.qsize()):

        return

    if (k <= 0):

        return

 

    Stack = []

 

    # put the first K elements

    # into a Stack

    for i in range(k):

        Stack.append(Queue.queue[0])

        Queue.get()

 

    # Enqueue the contents of stack

    # at the back of the queue

    while (len(Stack) != 0 ):

        Queue.put(Stack[-1])

        Stack.pop()

 

    # Remove the remaining elements and

    # enqueue them at the end of the Queue

    for i in range(Queue.qsize() - k):

        Queue.put(Queue.queue[0])

        Queue.get()

 

# Utility Function to print the Queue

def Print(Queue):

    while (not Queue.empty()):

        print(Queue.queue[0], end =" ")

        Queue.get()

 

# Driver code

if __name__ == '__main__':

    Queue = Queue()

    Queue.put(10)

    Queue.put(20)

    Queue.put(30)

    Queue.put(40)

    Queue.put(50)

    Queue.put(60)

    Queue.put(70)

    Queue.put(80)

    Queue.put(90)

    Queue.put(100)

 

    k = 5

    reverseQueueFirstKElements(k, Queue)

    Print(Queue)




OUTPUT:

50 40 30 20 10 60 70 80 90 100

CREDITS: https://www.geeksforgeeks.org/reversing-first-k-elements-queue/